1. Field of the Invention
The invention relates to a light reflective paint composition for use in light reflective articles in which diffuse light reflectance is desired. The invention further relates to a method for making the paint composition and to light reflective articles made using the paint composition.
2. Description of Related Art
Reflectors are used in numerous types of lighting fixtures to maximize the usable light, thus increasing the lighting efficiency. Maximization is achieved through a combination of reflecting and redirecting light generated by the lamp in a desired direction, and minimizing the light absorbed by the reflector. This is particularly important when the light fixture design includes a light cavity in which light rays are redirected multiple times within the cavity before exiting the light fixture as usable light. Lamps that use reflectors include tubular fluorescent lamps and light emitting diodes (LED).
Tubular fluorescent lamps emit light in 360 degrees around the lamp, thus the reflector redirects light from the back of the lighting fixture as usable light. LED light fixtures use a reflector in order to mix, obscure, or diffuse the discrete image(s) of individual LED lamps while maximizing useable lumens per given wattage. This reflector often consists of painted metal or highly polished aluminum. It is desirable to maximize the light reflected by the reflector and minimize the light absorbed by the reflector, as any light absorbed is unusable thereby decreasing the efficiency of the fixture.
Diffuse reflectance occurs when incident light is reflected by a surface such that the reflected light is scattered randomly or in a Lambertian fashion. By contrast, specular reflectance occurs when incident light is reflected at the same angle as the incident angle. Specular reflectors have been used in light fixtures to both direct light out of the fixture in a controlled or focused distribution and increase overall fixture efficiency. Diffuse reflectance is preferred in situations in which low glare is desired and/or in which it is desired to distribute light evenly over as broad an area as possible. White, diffuse reflectors are often used in room and office lighting to reduce specular glare.
The reflector surface includes metal components fabricated from coil steel or aluminum. Coil steel or aluminum is coated in continuous coil equipment with a paint typically containing titanium dioxide light scattering particles, and the coating is subsequently cured. The resulting coil surface has reflectance of up to about 90% and can be metal-formed into reflectors or light fixture bodies. Alternatively, powder coat paint is applied to light fixtures post metal-forming to provide a surface reflectance of up to 94%.
Lighting fixtures (e.g., luminaires, signage, daylighting applications, etc.) often have complex shapes including hemispherical domes and flanged edges, making it difficult to incorporate known reflective sheet. A reflective sheet can be laminated to steel and then formed into various geometries; however, this lamination step is not possible in all coil coating systems and requires an expensive adhesive to ensure proper lamination.